The annual Orionids meteor shower peaks this year on October 21st and the prospects are very good with the first quarter Moon will not significantly interfering. Generally regarded as a strong shower the Orionids or Orionid meteor shower is active between October 2nd and November 7th, although most activity is at peak date or a few days before or after it. In the past rates of up to 70 per hour have been observed but normally the shower is not so active, a figure between 20 and 25 is more the norm.
The Orionids parent comet is the most famous of all, Halley's Comet (1P/Halley). There is another annual shower associated with Halley's Comet, the Eta Aquariids in May. Of the two the Orionids is far more prolific.
Although Halley is now in the outer Solar System and will not return close to Earth until 2061 it's worth remembering that each Orionid meteor originates from a particle left over from Halley's Comet. Every observed Orionid is a small part of the famous comet streaking through and subsequently burning up in the Earth's atmosphere.
The radiant of the Orionids is located in the northeastern part of the constellation Orion, not far from the Gemini border. Since Orion straddles the celestial equator, the Orionids are one of the few annual showers that are well placed for observation from most locations on Earth (exception the polar regions).
What to expect in 2015
The best time to observe is after midnight between October 20th and 22nd. This year promises to be excellent with the first quarter Moon setting or appearing low down in west at the time the shower really kicks in. Although no major burst of activity is expected the Orionids are reliable with bright meteors and up to 25 per hour visible. They are also are fast meteors that hit the atmosphere at very high speeds of about 235,000 km/hour (145,000 miles/hour). To the eye they appear to streak across the sky. As with all annual meteors showers, it's best not to look directly at the radiant itself as the meteors can appear many degrees from it.
Orionids Data Table 2015
|Meteor shower name||Orionids|
|Meteor shower abbreviation||ORI|
|Activity||October 2nd -> November 7th|
|Peak Date||October 21st|
|RA (J2000)||6hr 20m|
|ZHR||20 to 25 (can vary between 20 and 70)|
|Notes||Most prolific meteor shower associated with Halley's Comet|
Comet 1P/Halley Data Table (at epoch February 17th, 1994)
|Classification||Halley-type comet (NEO)|
|Discoverer||Prehistoric, Edmond Halley first recognised the periodicity|
|Semi-major axis (AU)||17.8341|
|Orbital period (years)||75.3175|
|Longitude of ascending node (degrees)||58.4201|
|Last perihelion||February 9th, 1986|
|Next perihelion||July 28th, 2061|
|Notes||Halley's comet, the most famous of all comets|